WTB: Drifty A3 (ADC) board from 3458A

[TheSteve]

I'm looking for an A3 ADC board from a 3458A that has excessive drift - I don't care how bad the drift is but I'd prefer one that is not generating any kind of fault.
This is for testing a "cure" to the problem.

Shipping to US or Canada.

[coromonadalix]

You do know it can cost up to 1k$$ for a good one ??  EDIT   for a drifty one      no idea  sorry


Related threads about the A3  board

https://www.eevblog.com/forum/metrology/hp-3458a-ad-board-spare-part-availibilty-and-cost/

[TheSteve]

Yep, I need a bad board to further test a possible fix for the drift.
You can no longer purchase new or refurb A3 boards from Keysight.

[Kleinstein]

TiN did quite some tests and tries to fix it with his 1st bad ADC board. The conclusion was that the resistors in the ASCIC somehow started to dirft a bit. Not all resistors are acessible externally and replacing the ASIC completely can be tricky - there are switches with a difined ratio in the switch resistance. It is a bit more complicated than just multiple equal resistance switches. More like having 1:4:5:16 ratio in the switch resistance.

[TheSteve]

TiN did quite some tests and tries to fix it with his 1st bad ADC board. The conclusion was that the resistors in the ASCIC somehow started to dirft a bit. Not all resistors are acessible externally and replacing the ASIC completely can be tricky - there are switches with a difined ratio in the switch resistance. It is a bit more complicated than just multiple equal resistance switches. More like having 1:4:5:16 ratio in the switch resistance.

Yep, they are a bit of mystery. I have an A3 that was drifting at 0.4 to 0.8 ppm/day. After a bit of a "fix" it is now ~ 0.02 ppm/day. Could be a total fluke, maybe it won't last. I just want another board to try the process on.

[srb1954]

TiN did quite some tests and tries to fix it with his 1st bad ADC board. The conclusion was that the resistors in the ASCIC somehow started to dirft a bit. Not all resistors are acessible externally and replacing the ASIC completely can be tricky - there are switches with a difined ratio in the switch resistance. It is a bit more complicated than just multiple equal resistance switches. More like having 1:4:5:16 ratio in the switch resistance.

Yep, they are a bit of mystery. I have an A3 that was drifting at 0.4 to 0.8 ppm/day. After a bit of a "fix" it is now ~ 0.02 ppm/day. Could be a total fluke, maybe it won't last. I just want another board to try the process on.

I have a 3458A that is drifting quite badly:  averaging 2ppm per day, totalling 16ppm drift over 8 days running from a cold start. The indications are that the drift rate is even accelerating as time goes on.

Would you be prepared to publish your fix? I don't have a spare board so I can't ship the faulty one to you.

I might be interested to try your fix if I fail to get any compensation from the the vendor who described the 3458A as being in good condition in the auction listing.

[TheSteve]

Posting the details is on my "to-do" list. I was really hoping to see similar results with a second board before hand.

[coromonadalix]

Seems back on stock

https://www.keysight.com/my/partDetail/03458-66533

an Ebay auction
https://www.ebay.com/itm/134126678738?